Revenge of the Nerds has an off kilter example in that the nerd in question isn't exactly somone you would look at twice, but manages to get a hot cheerleader to dump her jock boyfriend because he's more...skilled and willing while the jock just used her as arm candy.

"How are you so good at that?" "All jocks think about is sports. All nerds think about is sex."

Eduardo (played by Andrew Garfield) in The Social Network.

Peter Parker, played by the adorable Toby McGuire, in the Spider-Man movies.

Finding someone on That Guy With The Glasses who isn't a cute geek would make for a much shorter list.

Linkara! The man is made of Geeky Turn Ons; extensive knowledge of comic books, likes Doctor Who, MST3K, Star Trek, and occasionally-obscure references, has glasses, wrote fanfiction, is an adorkable woobie, sings.... What isn't there to love!?